The effects of endogenous and dietary estrogens on colonic stem cells

描述（由申请人提供）：我们的数据支持内源性雌激素（E2）或含有雌激素化合物的化学保护饮食可降低结肠肿瘤发展风险的假设。这与人类研究一致，表明在结肠中暴露于雌激素可以防止恶性转化。尽管存在与雌激素治疗相关的担忧，但膳食植物雌激素可能提供一个合适的替代方案。事实上，流行病学数据表明，含有染料木素（Gen）等植物雌激素的大豆可以降低结肠癌的风险。关于假定的靶标，结肠的“成体”体细胞干细胞特别令人感兴趣，因为它们维持自我更新，是癌症启动突变的靶细胞。最近的证据表明，正常的肠道干细胞/祖细胞可以启动结肠肿瘤的发生，并推动癌症向转移方向发展。不幸的是，到目前为止，内源性和膳食雌激素对肠道干细胞信号传导的影响尚未确定。由于雌激素化合物可以影响调节结肠干细胞生态位和肿瘤进化的基因/介质，例如p53信号，我们的总体目标是进一步阐明E2和膳食Gen如何调节结肠干细胞在恶性转化的不同阶段。基于我们的实验结果，我们提出了两个特定的目标来确定内源性（E2）和膳食雌激素（Gen）如何影响结肠中的多能干细胞。Aim 1将使用高度新颖的干细胞特异性Lgr5-LacZ和Lgr5-EGFP小鼠，量化暴露于内源性和饮食来源的雌激素后，结肠癌发生起始和肿瘤阶段结肠隐窝中干细胞的数量和时空位置、DNA损伤和靶向凋亡。Aim 2将使用lgr5干细胞靶向p53缺失小鼠（Lgr5-EGFP-IRES-creERT2 x p53flox/flox）来确定p53在肠道干细胞中介导E2和Gen作用中的分子作用。拟议的研究具有高度创新性，将探索膳食雌激素化合物对结肠多能干细胞的生理作用。

DESCRIPTION (provided by applicant): Our data support the hypothesis that endogenous estrogen (E2) or a chemoprotective diet containing estrogenic compounds reduce the risk of colon tumor development. This is consistent with human studies demonstrating that exposure to estrogen in the colon protects against malignant transformation. Although there are concerns related to estrogen therapy, dietary phytoestrogens may provide a suitable alternative. Indeed, epidemiological data suggest that soy, containing phytoestrogens such as genistein (Gen), reduces colon cancer risk. With respect to putative targets, "adult" somatic stem cells of the colon are of particular interest because they sustain self-renewal and are target cells for cancer initiating mutations. Recent evidence indicates that normal intestinal stem/progenitor cells can initiate colon tumorigenesis and drive cancer progression towards metastasis. Unfortunately, to date, the effects of endogenous and dietary estrogens on intestinal stem cell signaling has not been determined. Since estrogenic compounds can impact genes/mediators that regulate the colon stem cell niche and tumor evolution, e.g. p53 signature, our overall goal is to further elucidate how E2 and dietary Gen modulate colonic stem cells at distinct stages of malignant transformation. Based on our experimental findings, we propose two specific aims to determine how endogenous (E2) and dietary estrogen (Gen) impact multipotent stem cells in the colon. Aim 1 will use highly novel stem cell specific Lgr5-LacZ and Lgr5-EGFP mice to quantify the number and spatio-temporal location of stem cells, DNA damage and targeted apoptosis in the colonic crypt at the initiation and tumor stages of colon carcinogenesis following exposure to endogenous and diet-derived estrogens. Aim 2 will use Lgr5-stem cell targeted p53 null mice (Lgr5-EGFP-IRES-creERT2 x p53flox/flox) to define the molecular role of p53 in mediating the effects of E2 and Gen in intestinal stem cells. The proposed studies are highly innovative and will explore the physiological actions of dietary estrogenic compounds on multipotent stem cells in the colon. PUBLIC HEALTH RELEVANCE: Epidemiological and clinical data suggest that consumption of plant derived, dietary phytoestrogens and/or exposure to endogenous estrogen reduces the risk of colorectal cancer in women. The proposed studies will define previously untested mechanisms by which dietary phytoestrogens and endogenous estrogen influence stem cell populations in the colon. In the long-term, these studies will provide the basis for developing new dietary strategies for reducing colon cancer risk and may lead to new recommendations for prevention of tumor reoccurrence in colon cancer patients.